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Calculate in matching units
If you know 46 + 27 = 73, then 46,000 + 27,000 = 73,000. You are counting thousands as units. Make sure both numbers use the same unit.
Split the second addend
For 468,000 + 27,000, first add 20,000, then 7,000. You get 488,000, then 495,000. The number 27,000 is not 27: the zeros show its thousands value.
Round, then compensate
For 256,400 + 9,900, add 10,000 and then remove the extra 100. You get 266,400 − 100 = 266,300. Remove the excess that you added.
Worked examples
468 000 + 27 000 = 488 000 + 7 000 = 495 000
We split the second addend into 20,000 and 7,000.
398 750 + 4 000 = 402 750
398 thousand plus 4 thousand is 402 thousand. The remainder 750 stays the same. Crossing 400,000 is expected.
Try it yourself
Your turn
Type the missing word, number, or sign. Spaces in large numbers are allowed. Try first, then open the explanation.
Two teams collect points: 186,500 and 24,900. Find their total by adding a round number.
See an example answer
186,500 + 25,000 − 100 = 211,400 points.
Check your knowledge
Choose one answer for each question. You can revise your answers and check again.
Answer key
- 790 000. 32 + 47 = 79, counted in ten-thousands.
- 301 500. 298 thousand + 3 thousand = 301 thousand.
- Add 20,000, then subtract 100. 20,000 is 100 more than the required addend.
- 1 000 000. 875 + 125 = 1,000 thousands.
- 429 018. The number of thousands changes; 018 remains.